What Is CAR-T Cell Therapy? Can It Really Treat Cancer, Who Is It Suitable For, and What Should You Know Before Treatment?

Normally, T-cells are a type of white blood cell that plays an important role in the body's immune system. Their function is to detect and eliminate abnormal cells, including cells infected with viruses or bacteria, cells that have undergone abnormal changes, and cancer cells, by recognizing antigens (Antigens) on the surface of those cells. However, certain cancer cells are able to evade detection by the immune system, making it difficult for T-cells to recognize them and preventing the immune system from mounting an effective response against the cancer. CAR-T Cell Therapy, or Chimeric Antigen Receptor T-cell Therapy, was developed to help overcome this limitation. T-cells are collected from the patient, or in some cases from a suitable donor, and genetically modified in a laboratory so that they express a special receptor called a CAR (Chimeric Antigen Receptor). This receptor enables the T-cells to recognize and bind more accurately to specific target antigens on the surface of cancer cells. The CAR-T Cells are then cultured and expanded until there are enough cells for treatment before being infused back into the patient's body through a vein.

Once CAR-T Cells enter the body, they use their specially engineered receptors to locate and bind to specific antigens on cancer cells, such as CD19, which is found on certain B-cell cancers, or BCMA, which is found in Multiple Myeloma. They then release important substances such as Perforin and Granzyme to destroy the cancer cells. At the same time, CAR-T Cells release Cytokines that help activate the immune system. These cells may also continue to multiply within the body for a period of time, which may contribute to longer disease control and more durable treatment responses in some patients.

CAR-T Cell Therapy can help treat certain types of cancer, particularly some blood cancers and lymphomas that have not responded to standard treatment or have relapsed. Although this treatment does not cure every patient, clinical evidence has shown that some patients can respond very well, achieve remission, and maintain treatment responses for several years.

According to long-term follow-up data from the ZUMA-1 study involving patients with refractory Large B-cell Lymphoma, Axicabtagene Ciloleucel, or Axi-cel, produced an overall response rate of 83% and a complete response rate of 58%. Some patients continued to maintain their treatment response over the long term (Neelapu et al., 2023). These findings suggest that CAR-T Cell Therapy may have the potential to provide durable disease control in certain patients.

Data from the ELIANA study, with approximately three years of long-term follow-up in pediatric and young adult patients with relapsed or refractory B-cell Acute Lymphoblastic Leukemia (B-ALL), found that Tisagenlecleucel helped many patients achieve remission, with some continuing to maintain a response for several years (Laetsch et al., 2023).

A review of long-term CAR-T Cell Therapy outcomes also indicated that CD19-targeted CAR-T Cells may help certain patients with B-cell cancers achieve long-term remission and may potentially lead to a cure in selected patient groups. However, treatment outcomes vary according to multiple factors. For BCMA-targeted CAR-T Cells in patients with Multiple Myeloma, treatment responses can be strong, although the duration of remission is generally shorter compared with CD19 CAR-T Therapy in B-cell cancers (Cappell & Kochenderfer, 2023).

Therefore, CAR-T Cell Therapy may be considered another treatment option for certain types of cancer, with the potential to help control disease severity and extend disease-free periods in some patients. However, outcomes may vary depending on factors such as the type of cancer, stage of disease, tumor burden, the patient's overall health, immune-system response, and complications that may occur after treatment.

The differences between CAR-T Cell Therapy and conventional cancer treatments can be summarized as follows:

• Treatment approach: CAR-T Cell Therapy is an immunotherapy that uses the patient's T-cells and modifies them to express a special receptor capable of specifically recognizing and destroying cancer cells. Standard cancer treatments vary in approach, including surgery to remove tumors, radiation therapy to destroy or inhibit cancer-cell growth, chemotherapy that acts on rapidly dividing cells, and Targeted Therapy for patients whose cancer has specific molecular targets that match the treatment.

• Suitable patient groups: CAR-T Cell Therapy is generally considered for patients with certain blood cancers or lymphomas that have not responded to standard treatment or have relapsed. Standard cancer treatments can be used for many different types of cancer depending on the individual patient's condition.

• Specificity for cancer cells: CAR-T Cell Therapy is designed to recognize specific target antigens on the surface of cancer cells. This makes it more specific to the target cells and may help reduce effects on unrelated normal cells. Chemotherapy, by contrast, affects rapidly dividing cells and may therefore also affect normal rapidly dividing cells such as blood cells, hair-follicle cells, and gastrointestinal lining cells. Radiation therapy may affect normal cells near the treatment area, while Targeted Therapy is more specific but can only be used in patients whose cancer has the relevant treatment target.

• Patients with certain blood cancers or lymphomas that have not responded to standard treatments or have relapsed.

• Patients whose overall health and major organ function, including the heart, lungs, liver, and kidneys, are suitable for treatment.

• Patients who are able to undergo close monitoring after treatment.

Whether CAR-T Cell Therapy is appropriate must be evaluated individually by a specialist physician.

CAR-T Cell Therapy is a personalized cancer treatment process consisting of several main steps:

• Pre-treatment health assessment: The physician assesses the type of cancer, stage of disease, previous treatment history, and the patient's overall physical readiness in order to develop an appropriate treatment plan.

• Collection of T-cells from the patient's blood: Blood is collected through a vein, and a blood-cell separation process called Leukapheresis is performed to isolate the T-cells. The remaining blood components are returned to the patient's body.

• Cell modification in the laboratory: The T-cells are modified to express CAR receptors, allowing them to recognize and bind more specifically to target cancer cells.

• Expansion of CAR-T Cells: After modification, the CAR-T Cells are cultured and expanded until there are sufficient numbers for treatment. This process may take several weeks. During this period, the physician may provide additional therapy to help control the disease while the cells are being prepared.

• Preparing the body before CAR-T Cell infusion: Patients usually receive low-dose chemotherapy before receiving CAR-T Cells. This helps reduce certain immune cells and prepares the body for the newly infused cells.

• CAR-T Cell infusion: The CAR-T Cells are administered back into the patient's body through a vein. The infusion typically takes approximately 30–45 minutes, although it may take longer in some cases.

• Post-treatment monitoring: After receiving CAR-T Cells, patients generally need to remain in a hospital or treatment center for approximately 1–2 weeks so that their response can be monitored closely. Once the patient's condition is stable, the physician may allow the patient to return home. However, some patients may be required to stay near the hospital or treatment center for an additional period according to the physician's judgment.

• It is a form of Targeted Immunotherapy and can act more specifically against cancer cells, helping reduce effects on unrelated normal cells.

• It uses the patient's own immune cells to fight cancer directly and involves an individualized treatment design, which may reduce the risk of rejection by the body.

• It provides another treatment option for patients with certain blood cancers, particularly when standard treatments have not worked or the cancer has relapsed.

• CAR-T Cells may multiply and remain active in the body for a period of time, potentially contributing to disease remission and longer disease-free periods in some patients.

Although CAR-T Cell Therapy provides an additional treatment option for some cancer patients, several important issues should be understood:

• Treatment outcomes differ between individuals and depend on factors such as the type of cancer, disease stage, overall health, previous treatments, and the body's response to CAR-T Cell Therapy.

• While waiting for CAR-T Cells to be prepared, some patients may receive bridging treatments such as chemotherapy, radiation therapy, Targeted Therapy, or Immunotherapy to help control the disease.

• Before receiving CAR-T Cells, patients usually receive low-dose chemotherapy to reduce certain immune-cell populations and prepare the body for CAR-T Cell expansion and activity.

• Side effects requiring close monitoring may occur, including Cytokine Release Syndrome (CRS), neurological toxicity or Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS), infection risk, fatigue, low blood-cell counts, or reduced immune function.

• Continuous medical follow-up is required after treatment. Physicians may schedule regular follow-up appointments for several months or years to evaluate treatment response, monitor for recurrence, and detect possible delayed complications.

CAR-T Cell Therapy can be an effective cancer treatment when performed under the supervision of an experienced medical team in an appropriately equipped medical facility. However, the treatment can cause side effects that require close monitoring, particularly during the early treatment period, including:

• Cytokine Release Syndrome (CRS): This occurs when the immune system becomes excessively activated after CAR-T Cell administration. Patients may develop fever, chills, low blood pressure, difficulty breathing, or fatigue. Severe cases may lead to failure of major organs.

• Neurological complications (ICANS): Symptoms may include confusion, dizziness, difficulty communicating, drowsiness, hand tremors, muscle twitching, balance problems, or seizures in some patients.

• Low blood-cell counts and low platelet counts: These conditions may cause fatigue, anemia, increased bleeding tendency, and easier bruising.

• Risk of infection: Immune function may be reduced during the early period after treatment. Patients therefore need to maintain strict hygiene and monitor themselves carefully. Any abnormal symptoms should be evaluated by a physician immediately.